[DevTools] Fix problem with loading source maps

Encode not utf8 chunk as base 64 and then decode it on frontend side.

BUG=611328
R=dgozman@chromium.org

Review-Url: https://codereview.chromium.org/2032013003
Cr-Commit-Position: refs/heads/master@{#397618}
(cherry picked from commit 72c30193f0804fff83ed73d92db7d5fc5df6b186)

Review URL: https://codereview.chromium.org/2039013002 .

Cr-Commit-Position: refs/branch-heads/2743@{#227}
Cr-Branched-From: 2b3ae3b8090361f8af5a611712fc1a5ab2de53cb-refs/heads/master@{#394939}
2 files changed